1. Field of the Invention
The present invention relates generally to microcolumns and, more particularly, to a microcolumn with a double aligner which is configured such that when an axis of an aperture of a limiting aperture is spaced apart from an original path of a particle beam, the path of the particle beam can be effectively compensated for in such a way that the path of the particle beam is aligned with the axis of the aperture of the limiting aperture by the double aligner.
2. Description of the Related Art
Generally, micro-particle beam columns (microcolumns) include a particle source (an emitting source) and electronic lenses which are operated using an electrostatic field and a magnetic field. The particle beam columns generate, focus and scan particle beams such as electron beams or ion beams. Electron columns using electron beams and ion beam columns using ion beams are examples of the particle beam columns. Such particle beam columns, particularly, electron columns, are used in an electron microscope, semiconductor lithography or in a variety of test devices, e.g., for checking a via hole/contact hole of a semiconductor device for defects, surface inspection and analysis of a specimen, mask inspection, for checking TFT (thin film transistor) wiring on a display device such as a TFT-LCD or an OLED, etc.
The electron column is a representative example of such a particle beam column. A micro-electron column which is an example of the electron columns for creating, focusing and scanning electron beams is manufactured based on an electron emitting source and a micro-electronic optical element that has an aperture having a diameter of 500 μm or less. Such a micro-electron column was introduced in 1980. The micro-electron column is an improved electron column in which fine elements are precisely assembled with each other to minimize optical aberration. By virtue of small size, a multiple electron column structure can be embodied in such a way that several micro-electron columns are arranged in parallel or in series. For this, a lens is manufactured using a silicone wafer through a semiconductor process, and an aperture portion of the lens is manufactured using a membrane through a microelectronic mechanical system (MEMS) process and may be used as an electrostatic lens.
FIG. 1 is a view illustrating the structure of a micro-electron column, showing an electron beam B irradiated into a particle emitting source (11, an electron emitting source), a source lens 12, a deflector 14 and a focus lens (15, an einzel lens) which are arranged in a row.
Typically, a microcolumn which is a representative example of the micro-electron column includes a particle emitting source (11, an electron emitting source) which emits electrons designated by the arrow, a source lens 12 which includes three electrode layers to emit, accelerate and control the electrons and forms an available electron beam using the emitted electrons, a deflector 14 which deflects the electron beam, and a focus lens (an einzel lens) 15 which focuses the electron beam on a specimen S. Generally, the deflector is disposed between the source lens and the einzel lens.
Typically, to operate the microcolumn, negative voltage (about −100 V to −2 kV) is applied to the particle emitting source (11, the electron emitting source), and appropriate voltages are applied to the electrode layers of the source lens 12. The einzel lens which is provided as an example of the focus lens 15 focuses the electron beam in such a way that external electrode layers which are disposed at opposite sides are earthed, and negative voltage (in a deceleration mode) or positive voltage (in an acceleration mode) is applied to an intermediate electrode layer. Based on the same operation distance, the level of focusing voltage of the deceleration mode is less than that of the acceleration mode. Synchronized deflecting voltage is applied to the deflector 14 to adjust the path of the electron beam and periodically apply the electron beam on the surface of the specimen. Controlling the electron beam, the electron lens such as the source lens or the focus lens includes at least two electrode layers each of which has in a central portion thereof an aperture having a circular shape or a predetermined shape so that the electron beam passes through the electrode layer. Typically, three electrode layers are used.
The micro-electron columns which have been illustrated as the representative electron beam column are classified into a singular micro-electron column which includes a single electron beam emitting source and electron lenses for controlling an electron beam emitted from the electron beam emitting source, and a multiple micro-electron column which includes electron lenses for controlling a plurality of electron beams emitted from a plurality of electron emitting sources. Multiple micro-electron columns are also classified into a wafer type micro-electron column which includes a particle beam emitting source having a plurality of particle beam emitting source tips provided on a single electrode layer such as a semiconductor wafer, and an electron lens in which a lens layer having a plurality of apertures is stacked on a single electrode layer, a combination micro-electron column in which a single lens layer having a plurality of apertures controls a particle beam that is emitted form each particle beam emitting source in the same manner as that of the single electron column, and an array type micro-electron column in which a plurality of single micro-electron columns are installed in a single housing. In the combination micro-electron column, only the particle beam emitting source is separately provided, but the lens can be used in the same manner as that of the wafer type micro-electron column.
In the microcolumn which is referred to as the particle beam column, a particle beam is generated from the particle beam source and is focused before scanning a specimen. Here, depending on the kind of specimen, a sample current method in which ions or electrons are detected may be used. In the sample current method, a conductive part of the sample is connected to the outside, and ions or electrons applied to the sample are directly detected so that the result can be directly checked from the outside. Such a sample current method can be used for checking a via hole/contact hole of a semiconductor device for defects, surface inspection and analysis of a specimen, for checking a TFT (thin film transistor) a TFT-LCD or an OLED for defects, etc.
However, the conventional microcolumn is problematic in that it may be partially deformed during a manufacturing process. Particularly, there is a difficulty in that the source lens into which particles emitted from the particle beam emitting source are first applied must precisely form the path of the particle beam to correctly focus the particle beam on the specimen S. That is, even when the emitted particle beam is injected into the source lens by the extractor of the source lens and is accelerated by the accelerator, if the path of the particle beam is not on the axis of the aperture of the limiting aperture, the particle beam cannot be correctly focused on the specimen. Particularly, because the aperture of the limiting aperture has a very small diameter, if the microcolumn including the limiting aperture and the source lens is incorrectly formed, it becomes difficult to apply the particle beam to the specimen.
If the application of the particle beam to the specimen is not correctly conducted, the operation efficiency of the microcolumn is reduced. In addition, the specimen is not precisely scanned. Therefore, the result of the inspection and analysis of the specimen is unreliable.